Single-crystal nanowires and liquid junction solar cells

Abstract

A method of making semiconducting oxide nanowire arrays on such as rutile is disclosed wherein a substrate is heated in the presence of a reaction mixture of non-polar solvent, semi-conductor metal oxide precursor source and strong acid to produce a nanowire array of a semiconducting oxide on the substrate. Dye sensitized solar cells that employ these nanowire arrays also are disclosed.

1 . A method of making semiconducting oxide nanowire arrays on a conducting oxide substrate comprising,
 loading a conducting oxide substrate into a reactor in the presence of a reaction mixture of one or more non-polar solvents, one or more semi-conductor metal oxide precursor sources and one or more strong acids, and   heating the reactor to produce a nanowire array of a semiconducting oxide on the substrate wherein the semiconducting oxide is selected from the group consisting of TiO 2 , WO 3 , CuO, ZnO, SnO 2 , V 2 O 5 , NiO, Nb 2 O 5 , Ta 2 O 5  and mixtures thereof.   
     
     
         2 . The method of  claim 1  wherein the conducting oxide substrate is selected from the group consisting of SnO 2 :In coated glass, SnO 2 :In coated polyethylene, SnO 2 :In coated polybutylene, SnO 2 :In coated polyethyleneterephtalate, SnO 2 :In coated copolymers of two or more of polyethylene, polybutylene, and polyethyleneterephtalate, SnO 2 :F coated glass, SnO 2 :F coated polyethylene, SnO 2 :F coated polybutylene, SnO 2 :F coated polyethyleneterephtalate, SnO 2 :F coated copolymers of two or more of polyethylene, polybutylene and polyethyleneterephtalate and mixtures thereof. 
     
     
         3 . A method of making rutile TiO 2  nanowire arrays on a conducting oxide substrate comprising,
 loading a conducting oxide substrate into a sealed reactor in the presence of a reaction mixture of one or more non-polar solvents, one or more Ti 4+  sources and one or more strong acids, and heating the reactor at about 1° C./min to about 30° C./min to a reaction temperature of about 150° C. to about 250° C. and holding at the reaction temperature for about 30 min to about 48 hours to produce a nanowire array of TiO 2  on the substrate.   
     
     
         4 . The method of  claim 3  wherein the conducting oxide substrate is selected from the group consisting of SnO 2 :In coated glass substrates, SnO 2 :In coated polyethylene, SnO 2 :In coated polybutylene, SnO 2 :In coated polyethyleneterephtalate, SnO 2 :In coated copolymers of two or more of polyethylene, polybutylene, and polyethyleneterephtalate, SnO 2 :F coated glass substrates, SnO 2 :F coated polyethylene, SnO 2 :F coated polybutylene, SnO 2 :F coated polyethyleneterephtalate, SnO 2 :F coated copolymers of two or more of polyethylene, polybutylene and polyethyleneterephtalate and mixtures thereof. 
     
     
         5 . A method of making coated TiO 2  nanowire arrays comprising
 immersing a SiO 2 :F coated glass substrate into an aqueous Ti 4+  precursor solution for about 2 to about 24 hours to yield a wetted substrate,   drying the wetted substrate at about 400° C. to about 500° C. for about 0.5 hrs to about 4 hrs to yield a TiO 2  coated substrate,   immersing the TiO 2  coated substrate into a reaction mixture that includes one or more nonpolar solvents, one or more Ti 4+  sources and one or more strong acids,   heating the reaction mixture at about 1° C./min to about 30° C./min to a reaction temperature of about 150° C. to about 250° C.,   holding at the reaction temperature for about 30 min to about 48 hours to produce a TiO 2  nanowire array on the TiO 2  coated substrate,   immersing the TiO 2  coated substrate bearing the TiO 2  nanowires into a solution of a Group VB metal to produce wetted TiO 2  nanowires on the substrate, and   drying the wetted nanowires at about 400° C. to about 500° C. for about 0.5 hr to about 4 hrs to yield TiO 2  nanowires having a coating thereon on the substrate.   
     
     
         6 . The method of  claim 5  wherein the coating is Nb 2 O 5 . 
     
     
         7 . A dye-sensitized solar cell comprising a rutile TiO 2  nanowire array made according to  claim 5 . 
     
     
         8 . A method of manufacture of a dye sensitized, liquid Junction solar cell comprising,
 treating a substrate bearing an array of dense packed semiconductor nanowires with a solution of an exciton acceptor dye to produce an array of exciton acceptor dye coated semiconductor nanowires,   infiltrating the array of acceptor dye coated semiconductor nanowires with a redox electrolyte that includes an electron donor dye,   attaching a counter-electrode to the array of coated semiconductor nanowires,   wherein the exciton acceptor dye and the exciton donor dye have a Forster radius there between, and   wherein spacings between the nanowires is about ±28% of the Forster radius.   
     
     
         9 . The method of  claim 8  wherein the semiconductor is rutile. 
     
     
         10 . The method of  claim 9  wherein the rutile is coated with Nb 2 O 5 . 
     
     
         11 . The method of  claim 9  wherein the nanowires are close packed. 
     
     
         12 . The method of  claim 9  wherein the exciton acceptor dye is ruthenium polypyridinium dye. 
     
     
         13 . The method of  claim 12  wherein the exciton donor dye is ZnPc-TTB. 
     
     
         14 . A dye sensitized, liquid junction solar cell comprising,
 a substrate bearing an array of dense packed exciton acceptor dye coated semiconductor nanowires,   a redox electrolyte that includes an electron donor dye interspersed between and in contact with the nanowires,   a counter-electrode attached to the array of coated semiconductor nanowires having an electron donor dye interspersed between and in contact with the nanowires,   the exciton acceptor dye and the exciton donor dye having a Forster radius there between, and   wherein spacings between the nanowires is about ±28% of the Forster radius between exciton acceptor dye and the exciton donor dye.   
     
     
         15 . The cell of  claim 14  wherein the semiconductor is rutile. 
     
     
         16 . The cell of  claim 15  wherein the rutile is coated with Nb 2 O 5 . 
     
     
         17 . The cell of  claim 15  wherein the nanowires are close packed. 
     
     
         18 . The cell of  claim 15  wherein the exciton acceptor dye is ruthenium polypyridinium dye. 
     
     
         19 . The cell of  claim 18  wherein the exciton donor dye is ZnPc-TTB.